1. Field of the Invention
This invention relates generally to improved method and apparatus for the generation of vibratory signals in liquid. More particularly, but not by way of limitation, this invention relates to an improved seismic generator apparatus and method that provides forore precise cyclic rate control and an extended operational life to the apparatus.
2. Description of the Prior Art
Various types of apparatus have been used in the past for generating the vibrations required for undersea exploration in seismic operations. For the most part, these devices provide some form of vibratory energy imparted into the water.
U.S. Pat. No. 3,349,367 issued Oct. 27, 1967 to Serge S. Wisotsky, contains a further discussion of the background and uses of such devices. The '367 patent also discloses a marine seismic generator that is similar to the generator disclosed herein. The apparatus of this invention is an improvement to the apparatus disclosed therein. While apparatus constructed in accordance with the '367 patent operated satisfactorily, apparatus constructed in accordance with the present invention is more efficient, provides more accurate control and response to changes of the cyclic rate.
Marine seismic generators are deployed from vessels and operate in conjunction with an array of electronic devices to receive the seismic signals. When operating, the devices are used many hours at a time because of the high costs involved. The generators must operate for literally millions of cycles without failures. Operating at 200 Hertz for 5 hours produces 3,600,000 cycles--and this is for only one five hour operating period. Thus, it is very important that the operating life of the generator be extended to the utmost.
The generator of this invnetion is also useful in generating vibratory signals in inland seismic operations when the generator is immersed in a pond, lake, mud pit or the like during operation. Such vibrations are sometimes utilized in connection with the vertical deployment of an array of geophones in a well bore or the like. The generator in such uses provides a point source of vibratory energy and the geophones sense the time occurrence and signal strength to provide geologists and geophysicist with information concerning the formations traversed and to be traversed by the well bore.
An object of the present invention is to provide improved apparatus for the generation of vibratory signals in liquid that has a longer operating life, is light, more compact, and provides for more accurate control of the cyclic rate of the vibratory signals.